Refrigeration control system



Aug. 5, 1941. c.' B. SPANGENBERG 2,251,503 REFRIGERATION CONTROL SYSTEMy Filed sept. so, 1938 i '2 sheets-sheet 1 so 28 l Aug. 5, -1941.

c. B. SPANGENBERG 2,251,503 REFRIGERATION CONTROL SYSTEM Filed Sept. 30,1938 2 Sheets-Sheet 2 Patented Aug. 5, 1941 UNITED STATES.` PATENTOFFICE REFRIGERATION CONTROL SYSTEM Charles B. Spangenberg, Minneapolis,Minn., as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application September 30, 1938, Serial No.232,574

, ze claims. `(cl. 62-4) This invention relates to refrigeration controlsystems and to improvements in the component parts thereof.

The primary object of this invention is to provide an improved controlsystem for a refrigwherein the compressor may be stopped when either thepressure on the low pressure side of the evaporator decreases to apredetermind low value or the pressure on the high pressure side of thererigerating apparatus increases to a predetermined high value andwherein an automatic resetting overload cut out 1s provided to stop thecompressor upon the occurrence of overload conditions. v.

Other objects and advantages will become apparent to those skilled inthe art upon reference to the accompanying specification, claims anddrawings, in which:

Figure l a diagrammatic illustration of one form of the control systemapplied to a refrigerating apparatus, i

Figures 2 and `3 arepiiodified forms of a portion of Figure 1 foraccomplishing substantially the same@ results asj'are accomplished inFigure Figure/f4 illustrates,'diagrammatically a modification ofthecontrol system Iolf Figure 1 for accomplishing "a slightly differentsequence of control, and u.

Figure 5 is a diagrammatic illustration of the manner of applying theoverload cut-out mechanism to the controlv system of applicationSeerating apparatus having evaporator means for refrigerant flows fromthe receiver Il through a liquid line i8 into the evaporator yII and theevaporated refrigerant is withdrawn from the evaporator II through a lowpressure or suction line I9 by the compressor I3. An expansion valvecontrols the supply of refrigerant to the evaporator II and it may be ofthe thermostatic type having a bulb 22 located at the discharge side ofthe evaporator and containing a volatile iluid and connected by acapillary tube 2| to the expansion valve. The construction thus fardescribed is conventional in the art and therev fore a furtherdescription thereof is not considered necessary it being sufficient tostate rial No. 101,107, filed September 16, 1,9436, by Wayland R.Miller.

Referringnow to Figure l the mediumto be Y conditioned or cooled by therefrigerating apparatus is shown to be air within an enclosure Il).

The medium in the enclosure I0 `is ycooled by a cooling coil preferablyin theformof an evaporator I I. Refrigerant is supplied to and withdrawnf,

from the evaporator I I by means of a refrigeratlng apparatus generallydesignated at I2 whichl may comprise a compressor fl3 operated byan Ielectric motor I4. 'The compressor I31delivers compressed refrigerantthroughahigh pressure line I5 into a condenser IG'and 'the condensedrefrigerant is collected in a receiver il, `[liquid controller generallydesignated at 25 operating in response to changes in pressure on thehigh pressure side of the refrigerating apparatus and pressureon the lowpressure side of the refrigerating apparatus, the latter being anindication or evaporator temperature. An overload cut-out mechanismgenerally designated at 2li-also controls the operation of thecompressor motor to protect the same against4 overload conditions,A

The temperature responsive controller 24 may comprise a bellows 28vcontaining a volatile fluid for operating a lever 29 'againstthe-action of anV adjustable tension spring 30. The lever 2!! inresponse to changes in temperaturel closes and opens a mercury switch3l.v For purposes of .i1-

lustration it is assumed that when the tempera.- I. ture of the mediumwithin the enclosure" llrises to 42 the mercury Switch 3l is tilted thevclosed position and when the yterfnperature',,de-l` creases to 40 vthemercury switchlll is tilte'd to the openposition@ The' controller 25against the action of an adjustable tension spring 38.,y'Qne-,eiidoithespring isfconnected tofthel lever-,551' andthe other endislconnect'ed a'nut f as srewftnreadedly'mont" dion; 'a Screwn. j By y`rotating tliegscrei'v 4 0', thgtension in ftheV spring' 38 ina'beadjuste'd'aiid hence the pressure set-gl ting of the bellows 34 may beadjusted. *The leverV mayv` corxl'prise` ajcsixl; 3'3.l in which is,mounted .abellows 34gco`nnected'by a', pipe 35 to the, low pressure `orsuction line'.l9,"4 The bellows' operates a lever 36. pivoted', at131,14

36 operates an arm 4| guided in a guide 42 and carrying at its upperextremity a screw 43. The screw 43 is adapted to engage a lever 44pivoted at 45 and carrying a mercury switch 46, the mercury switch 46being biased to the open position shown by its own weight. For purposesof illustration it is assumed that when the suction pressure rises to 35lbs. the screw 43 tilts the mercury switch to a closed position and assoon as the pressure on the low pressure side of the refrigeratingapparatus decreases a relatively small amount below this 35 lbs., thescrew 43 disengages the lever 44 to allow the mercury switch 46 to openif it is not latched closed at this time.

The controller 25 also includes a bellows -48 mounted in the casing 33and connected by a pipe 49 to the high pressure line |5. The bellows 48operates a lever 50 pivoted at 5| against the action of an adjustabletension spring 52. One end of the spring 52 is connected to the lever 50and the other end is connected to a nut 53 screw threadedly mounted on ascrew 54. By rotating the screw 54 the tension of the spring 52 isadjusted and hence the pressure setting of the bellows 48 is adjusted.Lever 50 operates an arm 55 guided in a guide 56 and carrying at itsupper extremity a screw 51. The screw 51 is adapted to engage a lever 58pivoted at 59 for closing a mercury switch 60, the mercury switch 60being biased to the open position shown by its own weight. For purposesof illustration it is assumed that when the pressure on the highpressure side of the refrigerating apparatus decreases to 140 lbs. thescrew 51 tilts the mercury switch 60 to a closed position and when thepressure rises a relatively small amount above this 140 lb. value thescrew |51 disengages the lever 58 to allow the mercury switch 60 to openproviding it is not latched closed at this time.

A latch means generally designated at 6| is utilized for latching themercury switch v46 closed during operation of the compressor after themercury switch 46 has been closed in the manner pointed out above. Thislatch means may comprise a bell crank lever pivoted at 63 and havingarms 62 and 64. Mounted on the same pivot 63 with the bell crank leveris a latch member 65 provided with an abutment 66 :for engaging the arm62 of the bell crank lever and also provided with an arm 61. 'I'he arms61 and 64 are provided with lugs 69 and 10 connected together by aspring 60 for holding the abutment 06 in engagement with the arm 62.

A latch means generally designated at 1| is also provided for themercury switch 69 for holding the same closed after it has once beenclosed in the manner pointed out above during the operation of thecompressor. This -latch means 1| may comprise a bell crank lever pivotedat 13 and having arms 12 and 14. A latch member 15 is pivoted on thepivot 13 and carries an abutment 16 for engaging the arm 12. The latchmember 1.5 also carries an arm 11, the arms 11 and 14 being providedwith lugs 19 and 90, respectively, connected together by a tensionspring 10 for holding the abutment 16 in engagement with the arm 12.

The latch means 6| and 1| are operated by an actuator 02 connected by arod 03 to an armature 05, the rod 03 being guided in a guide 04. A core96 and an operating coil 01 coact with the armature to raise thearmature 05 and hence the actuator 02 when the operating coil 91 isenergized.V Raising of the actuator 92 moves the latch means 6| and 1|outwardly to latch the mercury switches 46 and 60 closed after they bothhave been closed in the manner pointed out above.

The arm 4| operated in response to changes in pressure on the lowpressurev side of the evap orator carries a leg provided with a screw 9|for engaging the arm 61. For purposes of illustration it is assumed thatwhen the pressure on the low pressure side of the refrigeratingapparatus decreases to 10 lbs. the screw 9| will engage the arm 61 toovercome the spring 69 to release the latch member 65 from the lever 44to allow opening of the mercury switch 46. In a similar'manner the arm55 which is operated in response to changes in pressure on the highpressure side of the reirigerating apparatus is provided with a leg 92carrying a screw 93 for engaging the arm 11 of the latch means 1.|. Forpurposes of illustration it is assumed that when the pressure on thehigh pressure side of the refrigerating apparatus increases to lbs. thescrew 93 engages the arm 11 to move the same against the action of thespring 18 to disengage the latch member 15 from the lever 58 to allowopening movement of the mercury switch 60.

The overload cut-out mechanism generally designated at 26 may beprovided with control contacts 94 and 95 carried by a spring arm 96mounted on the bracket 91 and a pivoted lever 98, respectively. Pivotedlever 98 is provided with a cam surface 99 which coacts with abimetallic element |00 mounted on a bracket 0|. The bimetallic element|00 is heated by a heater |02 located in the energizing circuit for thecompressor motor I4. Upon the occurrence of an overload condition in thecompressor motor I4 the current flow through the heater element |02becomes excessive which warps the bimetallic element 00 to the leit andwhen the bimetallic element |00 has moved suillciently to the left thelever 98 moves downwardly to separate the contacts 94 and 95 tointerrupt the energizing circuit for the compressor motor. Thebimetallic element |00 carriesa contact |04 in an insulated manner whichengages a contact |05 carried by an arm |06 mounted on a bracket |01when the bimetallic element |00 tlexes suillciently far to the left toallow separation of the contacts 94 and 95. Engagement of the contacts|04 and |06 energizes an auxiliary heater |00 for ilexing upwardly abimetallic element |09 mounted on a bracket ||0. Upward movement of thebimetallic element |09 engages a lug on the lever 90 to reclose thecontacts 94 and 95. The heater |90 is so selected that a relatively longtime interval is caused to elapse before the-contacts 94 and 95 arereclosed and at this time the bimetallic element |00 has cooledsumciently to again latch the contacts 94 and 95 closed. Accordingly theoverload cut-out mechanism 99 opens the energizing circuit for thecompressor motor |4 upon the occurrence ot an excessive current ow inthe heater element |02 and automatically recloses the energizing circuitfor the compressor motor after the lapse of a predetermined timedinterval.

Power is supplied to the compressor motor |4 and to the control systemin general by means of line wires ||2 and ||3 leading from some sourceof power (not shown).

For purposes of illustration it is assumed that the temperature of themedium within the enclosure 0 increases to 42 to close the mercuryswitch 3|, that the pressure on the low pressure side of therefrigerating apparatus increases to through wire ||4, heater |02, wireIIE, lever 88..

contacts 95 and 94,arm 86, wire ||6, compressor motor |4, wire ||1,mercury switch 3|, wire ||8, mercury switch 60, wire H8, operating coil61, wire |20, mercury switch 46, and wire |2| back to the other linewire ||3.A Completion of this circuit energizes the compressor motor |4and hence places the refrigerating apparatus in operation and alsoenergizes the operating coil. 81 for raising the actuator 82 to-latchthe mercury switches 46 and 60 closed. 'I'he compressor motor |4 andhence the refrigerating apparatus remains in operation even though thepressure onV the low pressure side of the refrigerating apparatusdecreases below 35 lbs. and the pressure on the high pressure side ofthe refrigerating apparatus increases above 140 lbs. until such time asthe temperature within the enclosure Iv decreases to 40. When thetemperaturel within the enclosure |0 decreases to 40 the mercury switch3| is tilted to the 0H position to break the energizing circuit to thecompressor motor |4 and to deenergize the operating coil 81. The latchmeans 6| and 1| are thereupon released and the mercury switches 46 and60 are tilted to the off positions as shown. I'he rei'rigeratingapparatus can again be placed in operation only when the pressure on thelow pressure side of the refrigerating apparatus increases to 35 lbs.and the pressure on the high pressure side of the refrigeratingapparatus decreases to 140 lbs.

If during the operation of the refrigerating apparatus the pressure onthe low pressure side of the refrigerating apparatus decreases to 10lbs. before the temperature in the enclosure 10 de- Greases to 40 thescrew 9| releases the latch means 6| to allow the mercury switch 46 toopen. Opening of the mercury switch 46 breaks the energizing circuit forthe compressor motor |4 and deenergizes the operating coil 81 wherebyboth latch means 6| and 1| are' returned to the positions shown inFigure 1 to open the mercury switches 46 and 60. Here again therefrigerating apparatus lcan again be placed in operation only when thepressure on the low pressure side of the refrigerating apparatusincreases to 35 lbs. and the pressure on the high pressureV side oki;the refrigerating apparatus decreases to V140 l s.

If the pressure on the high pressure side of the refrigerating-apparatus should increase to 180 lbs.`before the temperature within theenclosure l0 decreases to 40 the screw 83v releases the latch means 1|to allow the mercury switch 60 to open. Opening of the mercury switch 60breaks the energizing circuit for the compressor Amotor |4 anddeenergizesthev operating coll 81 to release -both latch means 6| and.1| to allow opening of the mercury switches 46 and 60. After this hasoccurred the refrigerating apparatus may again be placed in operationonly when the pressure on the low pressure side of the refrigeratingapparatus increases; to 35 lbs. and the pressure on the high pressureside` of the refrigerating apparatus decreases to 140 lbs.

If during the operation of the refrigerating apparatus the current flowin the energizing circuit for the compressor motor |4 should becomeexcessive the control contacts 94 and 95 of the overload cut-outmechanism 26 will separate to break the energizingvcircuit for thecompressor lmotor I4 and deenergize the operating coil 81 to release thelatch means 6| and 1| and open the mercury.

switches 46 and 60. Accordingly following an overload condition therefrigerating apparatus can not againl be placed in operation until thepressure on the low pressure side of the refrigerating apparatusincreases to 35 lbs. and the pressure on the high pressure side of therefrigerating apparatus decreases to lbs. As

pointed out above the overload cut-out mechavnism 26 is automaticallyreclosed following the lapse of a predetermined timed interval so thatwhen the overload condition no longer exists the refrigerating apparatusmay be automatically restarted to maintain desired temperatureconditions within the enclosure |0.- Since it is impossible to start therefrigerating apparatus until the pressure on the high pressure side ofthe refrigerating apparatus decreases to a predetermined low value,illustratively 140 lbs., starting of the compressor against relativelyhigh head pressures is prevented and therefore the main cause foroverload conditions is eliminated in this system. Likewise therefrigeratlng apparatus is shut down when the pressure on the highpressure side of the refrigerating vapparatus increases to a,predetermined high value, say lbs., or the pressure on the low pressureside of the` refrigerating apparatus decreases to a low value of, say 10lbs. Accordingly in such a system it is perfectly satisfactory toutilize an automatic resettable overload cut-out mechanism since themajority of causes of overload conditions are eliminated by the controlsystem. About the only condition which will cause the overload cut-outmechanism to trip open is a low voltage condition which is not permanentin nature or extremely detrimental to the operation of compressor motor|4. From the above it is seen that the use of an automaticallyresettable (overload cut-out mechanism in this type of control system isextremely beneficial. Since it is impossible to start the compressoruntil the pressure on the low pressure side of the refrigeratingapparatus increases to 35 lbs., which may be a value corresponding tothe defrosting temperature of the evaporator Il, defrosting of theevaporator 4|| during each cycle of operation is assured.

Other means may be utilized for causing the latch means 6| and 1| tohold the switches 46 and 60 closed during operation of the refrigeratingapparatus and two of these means are shown in Figures 2 and 3.

In Figure 2 'a combined ball governor and Bowden wire arrangementgenerally designated at |30 is utilized for this purpose. A collar |3|is rigidly secured to the compressor motor shaft or compressor shaft |32for rotation therewith. Spring straps |33 carrying weights |34 areconnected to the collar |3| and to a collar |35 slidably mounted on theshaft |32. Upon rotation of the compressor motor or compressor shaft |32the weights |34 fly outwardly tofmove the collar |35 towards the left.The collar |35 is provided with a groove |36 for receiving a pin |31carried by a yoke |38. Secured to the yoke |38 is a wire |38 curyswitches 46 and 60 closed during the operation of the refrigeratingapparatus. The combined ball governor and Bowdenwire arrangementtherefore provides exactly the same operation as the electromagneticactuator of Figure 1 and therefore a further description is notconsidered necessary.

In Figure 3 the actuator 82' is operated by a iuid pump arrangementgenerally designated at E44. The actuator 82 is connected by a rod |45to a diaphragm |46 which is clamped to a pressure chamber |41 by a ring|48. A uid line |49 c onnects the pressure chamber under the diaphragm|46 to the discharge side of a gear pump |50 which is operated by thecompressor motor shaft or the compressor shaft. Fluid is supplied to thegear pump |50 by a supply line |5| leading from a sump |42. Accordinglywhen the compressor is placed in operation the gear -pump forces thediaphragm |46 and hence the actuator 82 up- Y wardly to cause the latchmeans 6| and 1| to latch the mercury switches 46 and 60 closed duringthe operation of the refrigerating apparatus. When the refrigeratingapparatus shuts down the uid in the pressure chamber leaks balclrthroughthe gear .pump |50 to the sump|52 to allow the' to 35 1bs. a circuit isthereupon completed from Completion of this circuit causes operation ofthe compressor motor I4 and energization of the oppressure on the highpressure side of the refrigv erating apparatus decreases to 142 lbs. themercury switch 60 and the latch means 1| may be omitted as isillustrated in Figure 4. In Figure 4 the bellows 48 which'is operated inaccordance with changes in pressure on the high pressure side of therefrigerating apparatus operates aA lever pivoted at |56 against theaction of an adjustable tension spring |51. One end of the tensionspring |51 is'connected to the lever |55 and the other end is connectedto a nut |58 screw threadedly mounted on a screw |59. By rotating thescrew |59 the tension in the spring |51 may be adjusted and hence thepressure setting of the bellows 48 may be adjusted. Lever |55 carries ascrew |60 which is adapted to engage the arm 61 of the latch means 6|,for example, when the pressure on the high pressure side of therefrigerating apparatus increases to 180 lbs.

Accordingly in the construction shown in Figure 4 the mercury switch 46is closed when the pressure on the low pressure side of therefrigerating apparatus increases to 35 lbs. and is heldclosed by thelatch means 6| during operation of the compressor. If either thepressure on the low pressure side of the refrigerating apparatus de'-creases to 10 lbs. to cause the -screw 9| to engage the arm 61 or thepressure on the high pressure side of the refrigerating apparatusincreases to 180 lbs. to cause the screw |60 to engage the arm 61 thelatch means 6| is released to allow the mercury switch 46 to open.

Power is supplied to the compressor motor I4 in Figure 4 by line wires|62 and |61 leading from some source of power (not shown). Assume nowthat the temperature within the enclosure increases vto 42 to close themercury erating,coi1 81 to latch the mercury switch 46 closed. Thecompressor motor |4 will thereupon remain in operation until either thetemperature within the enclosure should decrease to 40 or the pressureon the low pressure side of the refrigerating apparatus should decreaseto 10 lbs. or the pressure on the high pressure side of therefrigerating apparatus should increase to 180 lbs. or an overloadcondition should occur.

The overload cut-'out mechanism of this invention may also be applied tothe control system shownand described in application Serial No. 101,107,led Sept. 16, 1936, by W. R. Miller to accomplish substantially the sameresults as are accomplished in the control system of Figure 1.

'The application of the overhead cut-out mecha- I 'nism 26 to thecontrol system of the W. R. Miller application is diagrammaticallyillustrated in Figure 5. The compressor motor I4 is here controlled by arelay or starter generally designated at |10 and comprising an operatingcoil |1| for operating switch arms |12 and |13 with respect to,contacts|14 and |15. When the operating coil |1| is energized the switch arms|12 and |13 are moved into engagement with their respective contacts |14and |15 and when the operating coil |1| is deenergized the switch armsare moved out of engagement with their respective contacts by means ofsprings gravity or other means (not shown).

Contacts |16 and 11 are normally closedbut are open when the pressure onthe high pressure side of the refrigerating apparatus increases to 180lbs. and contacts |18 and |19 are normally open butare moved to a closedposition when the pressure on the high pressure side of therefrigerating apparatus decreases to 140 lbs. Contacts and |8| arenormally closed but are moved to an open position when the pressure onthe low pressure side of the refrigerating apparatus decreases to 10lbs. and contacts |82 and |83 are normally open but are moved to aclosed position when the pressure on the low pressure side of therefrigerating apparatus increases to 35 lbs. The mercury switch |84 isoperated in accordance with variations in temperature being controlledand is moved to a closed position when the temperature increases to 42and is moved to an open position when the temperature decreases to 40.Control contacts 94 and 95, the auxiliary contacts |04 and |05, the mainheater |02 and the auxiliary heater |08 of the overload cut-outmechanism |26 are schematically shown in Figure 5. Power is supplied tothe control system of Figure 5 by means of 'line wires |81 and |88leading from some source of power (not shown).

Assume now that the temperature to be controlled increases to 42 toclose the mercury .switch |84, that vthe pressure on the high pressureside of the refrigerating apparatus decreases to lbs. to cause contacts|18 and |19 to engage and that the pressure on the low pressure side ofthe refrigerating apparatus increases to 35 lbs. to cause the contacts|82 and |83 to engage. This completes a. circuit from the line wire |61through wire |89, control contacts 9.4 and 95 ot theoverload cut-outmechanism 28, wire |90, contacts |18 and |11, wire |9I, mercury switch|84, wire |92, contactsV |80 and |8|, wires |93 and |94, contacts |83and |82, wire |95, contacts "|19 and |18, wires |96 and |91, operatingcoil |1 I, and Wires |98 and |99 back to the other line wire |88.Completion of this circuit energizes the operating coil |1| to move the'switch arms |12 and |13 into engagement with their respective 10contacts |14 and |15.

Movement of the switch arm |12 into engagement with the contact |14completes a circuit from the line wire |12 through heater element |02,contact |14, switch arm |12, wire 200, com- 15 pressor motor I4 andwires 20| and |99 back to the other line wire |88. Completion of thiscircuit causes operation of the compressor motor |4.

Movement of-the switch arm |13 into engagement with the contact |15completes a maintain- 20 ing circuit for the operating coil |1| which isindependent pf the contacts |18 and |19 and the contacts |82 and |83.'I'his circuit may be traced from the line wire |81 through wire |89,contacts 94 and 95, wire |90, contacts |18 and |11, wire 25 upon theoccurrence of an excessive current flow through the heater |02 or thepressure on the 35 high pressure side of the refrlgerating apparatusincreases to 180 lbs. or the temperature being controlled decreases toor the pressure on' the low pressure side of the refrigerating apparatusdecreases to 1-0 lbs. When' any of these con- 40 tingencies occur therefrigerating apparatus can-lI not again be restarted until the mercuryswitch |84 is closed upon a call for cooling, the control contacts 94and 95 of the overload cut-out mechanism 26 are reclosed, the -pressureon the high 45 pressure side of the refrigerating apparatus decreases to148 lbs. and the pressure on the low pressure side of the refrigeratingapparatus increases to 35 lbs. Accordingly the sequence of operation issubstantially the same as that of -50 the construction shown in Figure 1although the construction of the two systems is entirely diierent. InFigure 5 the control contacts 94 and 95 of theoverload cut-out mechanismare located in a pilot circuit while in Figure 1 they are shown 55 to bein the energizing circuit of the compressor motor.

Although for purposes of illustration several forms of this inventionhave been disclosed other forms thereof may become apparent to thoseskilled in the art upon reference to this disclosure and therefore thisinvention is to be limited only by the scope of the appended claims andprior art.

I claim as my invention:

1. In a control system for a refrgerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor, means responsive to a/condition which is a measure ofevaporator temperature for closing the switch means whenvthe evaporatortemperature rises to a predetermined high value foroperating thecompressor, and latch means operated as an incident Completion of thiscircuitlmaintains the 30 to operation of thecompiessor for holding theswitch means closed as long as the compressor remains in operation.

2. In a control system for a refrigerating apparatus includingacompressor and evaporator means-for cooling a medium, the combinationof, means including switch means for `controlling the operation of thecompressor, means responsive to a condition which is a measure ofevaporator temperature for closing the switch means when the levaporatortemperature rises to a predetermined high value for operating thecompressor,

latch means operated as an incident to operationV of the]y compressorfor holding the switch means closed as long as the compressor remains inoperation, and means operated by said condition responsive means whenthe evaporator temperature decreases to a predetermined low value forvreleasing said latch means to open said switch means and stop operationof the compressor.

3. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means f or controlling the operation of thecompressor, means responsive to the pressure on the high pressureside.oi

the refrigerating apparatus for closing the switch meansfwhen thepressure decreases to a predetermined low value for Operating thecompressor, and latch means operated as an incident to Voperation of thecompressor for holding the switch means closed as long as thecompressor/ remains in operation.

4. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor,.v means responsive to the pressure on the high 'pressureside of the reirigerating apparatus for closing the switch means whenythe pressure decreases to a. predetermined low value for operating thecompressor, latch means operated as an incident to operation of thecompressor for holding the switch means closed as long as the compressorremains in operation, and means operated by said pressure responsivemeans when the pressure increases to a predetermined high value forreleasing said 4|latch means to open said switch means and stopoperation of the compressor.

5. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor, control means responsive to a condition which is a measureof evaporator temperature, means controlled'by said control means forclosing said switch means when the evaporator temperature rises to apredetermined high value for operating the compressor, latch meansoperated as an incident to operation of the compressor for holding theswitch nieans closed as long as the compressor'remains in operation,control means responsive to the pressure on the high pressure side ofthe refrigerating apparatus, and means controlled by said last mentionedcontrol means for releasing said latch means when the pressure on thehigh pressure side of the refrigerating apparatus increases to apredetermined high value to open said switch means andv stop operationof the compressor.

6. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor, control means responsive to .a condition which is a measureof evaporator temperature, means controlled by switch means closed aslong as the compressorV remains in operation, control means responsiveto the pressure on the high pressure side of the refrigeratingapparatus, and means controlled by both of said control means forreleasing said' latch means when either the evaporator temperaturedecreases to a predetermined low value or the pressure on the highpressure side of the refrigerating apparatus increases to apredetermined high value to open said switch means and stop operation ofthe compressor.

'7. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor, control means responsive to a condition which is a measureof evaporator temperature, control means responsive to the pressure onthe high pressure side of the refrigerating apparatus, means controlledby said control means for closing said switch means when both theevaporatortemperature increases to a predetermined high value and thepressure on the vhigh pressure side of the refrigerating apparatusdecreases to a predetermined low value,

' and latch means operated as an incident to operation of the compressorfor holding the switch means closed as long as the compressor remains inoperation.

8. 'In a control system for a. refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including switch means for controlling the operation of thecompressor, control means responsive to a condition which is a measureof evaporator temperature, control means responsive to the pressure onthe high pressure side of the refrigerating apparatus, means controlledby said control means for closing said switch means when both theevaporator temperature increases to a predetermined high value and thepressure on the high pressure side of the refrigerating apparatusdecreases to a predetermined low value, latch means operated as anincident to operation of the compressor for holding the switch meansclosed as long as the compressor remains in operation, and meanscontrolled by said control means for releasing said latch means wheneither the evaporator temperature4 decreases to a predetermined lowvalue or the pressure on the high pressure side of the refrigeratingapparatus increases to a predetermined high value to open said switchmeans and stop operation of the compressor.

9. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including rst and second switch means arranged in series forcontrolling the operation of the compressor, first control meansresponsive to a condition which is a measure of evaporator temperaturefor closing the rst switch means when the evaporator temperature risesto a predetermined high value, second control means responsive to thepressure on the high pressure side of the refrigerating apparatus forclosing the second switch means when the pressure decreases to apredetermined low value, and latch means operated as an incident tooperation of the compressor for holding the switch means closed as longas the compressor remains in operation.

10. In a control system for a refrigeratingapparatus including `acompressor and evaporator means for cooling a medium, the combinationof, means including iirst and second switch means arranged in series forcontrolling the operation of the compressor, first control meansresponsive to a condition which is -a measure of evaporator temperaturefor closing the first switch means when the evaporator temperature risesto a predetermined high value, second control means responsive to thepressure on the high pressure side of the refrigerating apparatus forclosing the second switch means when the pressure decreases to apredetermined low value, latch means operated as an incident tooperation of the compressor for holding the switch means closed as longas the compressor remains in operation, and means operated by both ofsaid control means for releasing said latch means when either theevaporator temperature decreases to a predetermined low value or thepressure on the high pressure side of the refrigeratingapparatusincreases to a predetermined high value.

1l. In a control system for aI refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including rst and second switch means arranged in series forcontrolling the operation of the compressor, iirst control meansresponsive to a condition which is a measure of evaporator temperaturefor closing the first switch means when the evaporator temperature risesto a predetermined high value, second control means responsive to thepressure on the high pressure side of the refrigerating apparatus forclosing the second switch means when the pressure decreases to apredetermined low value, and latch means for each switch means andoperated as an incident to operation of the compressor for holding their.respective switch means closed as long as the compressor remains inoperation.

l2. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including rst and second switch means arranged in series forcontrolling the operation of the compressor, rst control meansresponsive to .a` condition which is a measure of evaporator temperaturefor closing the iirst switch means when the evaporator temperature risesto a predetermined high value, second control means responsive to thepressure on the high pressure side of the refrigerating apparatus forclosing the second switch means when the pressure decreases to apredetermined low value, latch .means for each switch means and operatedas an incident to operation of the compressor for holding theirrespective switch means closed as long as the compressor remains inoperation, means operated by the first control means for releasing thelatch means of the rst switch means when the evaporator temperaturedecreases to a predetermined low value to open the rst switch means, andmeans operated by the second control means for releasing the latch meansof the second switch means when the pressure on the high pressure sideof the refrigerating apparatus increases to a predetermined high valueto open the second switch means.

13. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the .combinationof,

nrst switch means, first control means responsive to a condition of themedium being cooled which is a measure of the cooling requirements bythe medium for closing the first switch means upon a demand for coolingand for opening the first switch means when the cooling demand issatisfied, second switch means, secondvcontrol means responsive to acondition which is a measure of evaporator temperature for closing thesecond switch means when the evaporator temperature rises to apredetermined high value, means controlled by the rst and second switchmeans for operating the compressor when both switch means are closed,and latch means operated as an incident to operation of the compressorfor holding the second switch means closed as long as the compressorremains in operation.

14. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, first switch means, first control means responsive to a condition ofthe medium being cooled which is a measure of the cooling requirementsof the medium for closing the first switch means upon a demand forcooling and for opening the rst switch means when the cooling demand issatisfled, second switch means, second control means responsive to acondition which is a measure of vrises lto a' predetermined high value,means controlled by the first and second switch means for operating thecompressor when, both switch means are closed, latch means operated asan incident to `operation of the compressor for holding the secondswitch means closed as long .as the compressor remains in operation, andmeans controlled by the second control means for releasing the latchmeans when the evaporator temperature decreases to a' predetermined lowvalue to open the second switch means.

15. In a vcontrol system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, first switch means, first control means 'responsive to a conditionof the medium being cooled which is a measure of the coolingrequirements of the medium for closing the first switch means upon ademand for cooling andffor opening the iirst switch means when thecooling demand is satisfied, second switch means, secon control meansresponsive to the pressure on the high pressure side of therefrigeratingapparatus for closing the second switch means when thepressure decreases to a predetermined low value, means controlled by therst and second switch means for operating the compressor when bothswitch means are closed, latch means operated as an incident tooperation of the compressor for holding the second switch means closedas long as the compressor remainsv in operation, and means controlled bythe second control means for releasing the latch means when the pressureon the high pressure side of thevrefrlgerating apparatus increases to apredetermined high value to open the second switch means.

16. In a control system for a refrigerating ap-y paratus including acompressor and evaporator means for cooling a medium, the combinationof, first switch means, rst control means responsive to a condition ofthe medium being cooled which is a measure of the cooling requirementsof the medium for closing the first switch means upon a demand forcooling'and for opening the first switchmeans when the cooling demand issatisfied, second switch means. second control means responsive to acondition which is a measure of evaporator temperature for closing thesecond switch means when the evaporator temperature rises to apredetermined high value, means controlled by the first and secondswitch means for operating the compressor when both switch meansareclosed, latch means operated as an incident to operationof thecompressor for holding the second switch means closed as long as thecompressor remains in operation, third control means responsive to thepressure on the high pressure side of the refrigerating apparatus forreleasing the latch means when the pressure increases to a predeterminedhigh value to open the second switch means.

17, In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combination offirst switch means, first control means responsive to a condition of themedium being cooled which is a measure of the cooling requirements ofthe medium for closing the first switch means upon a demand for. coolingand for openingthe first switch meansv when the cooling demand issatisfied, second switch means, second control means responsive to acondition which is a measure of evaporator :temperature for closing thesecond switch means when the evaporator temperature rises to apredetermined high value, means controlled by the first and secondswitch means for operating the compressor when both switch means areclosed, latch means operated asan incident to operation of thecompressor for holding the second switch means closed as long as thecompressor remains in operation, means controlled by the second controlmeans for releasing the latch means when the evaporator temperaturedecreases to a predetermined low value to open the second switch means,third control means responsive to the pressure on the high pressure sideof the refrigerating apparatus for releasing the ylatch means when thepressure increases to a predetermined high value to open the secondswitch means.

18. In a control system for a refrigerating apparatus including alcompressor and evaporator means for cooling a medium, the combinationof,

` iirst switch means, iirst control means responsive to a condition ofthev medium being cooled which is a measure of the cooling requirementsof the medium for closing the rst switch means upon a demand for coolingand forropening the first switch means when the cooling demand issatisfied, second switch means, second control means responsive to acondition which is a measure lof evaporator temperature, third controlmeans responsive to the pressure o the high pressure side of therefrigerating apparatus, means controlled by the second and thirdcontrol means to close the second switch means when bothv the evaporatortemperature increases to a predetermined high value and the pressure onthe high pressure side of the refrigerating apparatus decreases to apredetermined low value, means evaporator temperature decreases to apredetermined low value or the pressure on the high pressure side of therefrigerating apparatus increases to a predetermined high value to openthe second switch means. I

19. In a control system for a refrigerating apparatus having anelectrically operated compressor and evaporator means for cooling amedium, the combination of, an energizing circuit for the electricallyoperated compressor, means including control means responsive to thepressure on the high pressure side of the refrigerating apparatus forclosing the energizing circuit and operating the compressor only whenthe pressure on the high pressure side of the refrigerating apparatusdecreases to a predetermined low value wherebystarting of the compressoragainst high head pressures is prevented, switch means for controllingthe energizing circuit, means responsive to the current flow through theenergizing circuit for tripping open the switch means for opening theenergizing circuit in response to an excessive current ow, and meansoperative upon opening of the switch means for automatically reclosingthe switch means after a time interval has elapsed.

20. In a control system for a refrigerating apparatus having anelectrically operated compressor and evaporator means for cooling amedium, the combination of, an energizing circuitvfor the electricallyoperated compressor, control means responsive to the pressure on the lowpressure side oi'` the refrigerating apparatus, control means responsiveto the pressure on the high pressure side of the reirigeratng apparatus,means controlled by said control means to close the energizing circuitand operate the compressor only when the pressure on the low pressureside of the refrigerating apparatus increases to a predetermined highvalue and the pressure on the high pressure side of the reirigeratingapparatus decreases to a predetermined low value and for maintaining theenergizing circuit closed and the compressor in operation until eitherthe pressure on the low pressure side of the refrigerating apparatusdecreases to a predetermined low value or the pressure on the highpressure side of the reirigerating apparatus increases to apredetermined high value, overload cut-out means for controlling theenergizing circuit including con-v trol means tripped open upon theoccurrence of an excessive current ow through the energizing circuit foropening the energizing circuit, and means operative upon opening of thecontrol means for automatically reclosing the control means followingthe lapse of a predetermined time interval.

21. 'In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, rst switch means, first control means responsive to the condition'ofthe medium being cooled for closing the rst switch means upon a demandfor cooling and for opening the iirst switch means when the coolingdemand is satisied, second switch means, second control means responsiveto a condition which is a measure of evaporator temperature, thirdcontrol means responsive to the pressure on the high pressure side ofthe refrigerating apparatus, means controlled by the second and thirdcontrol means to close the second switch means when both the evaporatortemperature increases to a predetermined high value and the pressure onthe high pressure side of the reirig'erating apparatus decreases to apredetermined low value, means controlled by the iirst and second switchmeans for operating the compressor when both switch means are closed,latch means operated as an incident to operation of the compressor forholding the second switch means closed as long as the compressor remainsin operation, means controlled by the second and third control means forreleasing the latch means when either the evaporator temperaturedecreases to a predetermined low value or the pressure on the highpressure side increases to a predetermined high value to open the secondswitch means, overload cut-out means for the compressor including switchmeans for additionally controlling the operation of the compressor,means for latching the switch means closed, means responsive to acompressor overload condition for releasing the last mentioned latchmeans to cause the last mentioned switch means to open for stoppingoperation of the compressor, and means operative upon opening of thelast mentioned switch means for automatically reclosing the switch meansand latching the same closed following the lapse 'of a predeterminedtime interval.

22. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, means including control means responsive to a condition which is ameasure of evaporator temperature for starting operation of thecompressor only when the evaporator temperature rises to a predeterminedhigh value and means operated directly and mechanically by thecompressor for maintaining the compressor in operation.

23. Ina control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, lthe combinationof,

iirst control means responsive to a condition of the medium being cooledwhich is a measure of the cooling requirements of the medium, secondcontrol means responsive t0 a condition which is a measure of evaporatortemperature, means controlled by both control means for startingoperation of the compressor only when the iirst control means demandscooling and the evaporator temperature increases to a predetermined highvalue, and means operated directly and mechanically by the compressorfor maintaining the compressor in operation until the first controlmeans becomes satisiied.

24. In a control system for a reirigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, iirst switch means, iirst control means responsive to a conditionyof the medium being cooled which is a measure of the coolingrequirements of the medium for closing the first switch means upon ademand for cooling and for opening the rst switch means when the coolingdemand is satistled, second switch means, second control meansresponsive to a condition which is a measure of evaporator temperaturefor closing the ,second switch means when the evaporator temparatusincluding a compressor and evaporator means for cooling a medium, thecombination of, first control means responsive to a condition of themedium being cooled which is a measure of the cooling requirements ofthe medium, second control means responsive to a condition which is ameasure of evaporator temperature, means controlled by both controlmeans for starting operation of the compressor only when the irstcontrol means demands cooling yand the evaporator temperature increasesto a predetermined high value and means actuated by operation of thecompressor for maintaining the compressor in operation until the firstcontrol means becomes satisfied.

26. In a control system for a refrigerating apparatus including acompressor and evaporator means for cooling a medium, the combinationof, first control means responsive to a condition of the medium beingcooled which is a measure of the cooling requirements of the medium,second control means responsive to a condition which is a measure ofevaporator temperature, means controlled by both control means forstarting opera tion of the compressor only when the first control meansdemands cooling and the evaporator temperature increases to apredetermined high value and means actuated by operation of thecompressor for maintaining said second control means in compressoroperating position until the rst control means becomes satisfied.

CHARLES B. SPANGENBERG.-

